As the molecular genetic factors on human disorders became clearer, study for gene therapy has been increasingly emphasized recently. Gene therapy is intended to express DNA on targeted regions. The important things for gene therapy are how to deliver the DNA to the targeted region, and how to effectively introduce the DNA into the targeted region and express functionally the DNA on the region. As a vector for introducing foreign DNA, many viruses including retrovirus, adenovirus, and herpesvirus, which are altered to transfer therapeutic gene, have been used for clinical trials on human gene therapy. However, the risks of infection and immune reaction still remain.
As a non-viral vector for transferring DNA into cells, for example, dioleoyloxypropyl trimethylammonium, which is a cationic lipid (Felgner et al., Proc. Natl. Acad. Sci. USA, 84, 7413-7417, 1987), has been commercialized as Lipofectin (registered trademark). As a synthetic polymer for vector, polyethyleneimine has been commercialized as Exogen.
DNA-lipid complexes are described in Felgner et al., PNAS, 84 (1987) 7413.
Generally, nucleic acids are not stable within a living body and are decomposed by a certain type of enzyme.